2-mm Waveband electron paramagnetic resonance spectroscopy of conducting polymers

4,5-Bis(trifluoromethyl)-1,2,3-trithiolylium hexafluoroarsenate, which contains the 7π F3C[graphic omitted]CF3˙+ radical cation, the first example of a cationic carbon–sulfur heterocycle, has been prepared and characterised. It was prepared as a purple solid in 90% yield by the reaction of F3CCCCF3 with a 1 : 1 mixture of S4(AsF6)2 and S8(AsF6)2 in SO2 at 50 °C for 2 weeks. Small amounts of a homopolyatomic sulfur cation (probably S82+) were removed by work-up with fresh F3CCCCF3 and AsF5 in SO2 at 50 °C for 8 d. The F3C[graphic omitted]CF3AsF6 was characterised in the solid state by chemical analyses, IR, mass spectrometry [M+ at m/z 258 (100%)] and X-ray crystallography. The crystal structure consists of layers containing both monomeric, planar F3C[graphic omitted]CF3˙+ radical cations and AsF6– anions [space group Pnma, a= 12.241(4), b= 8.232(5), c= 37.39(3)A, Z= 12 and R= 0.086]. A powder photograph of the bulk product correlated with the single-crystal data, and a variable-temperature magnetic susceptibility study indicated that F3C[graphic omitted]CF3AsF6 is a paramagnetic solid, exhibiting ordinary Curie–Weiss behaviour, µ= 1.68, θ=–0.6 K (µ= 2.1 in SO2 solution at room temperature). The ESR spectrum of F3C[graphic omitted]CF3˙+ in SO2 is identical to that previously reported for F3C[graphic omitted]CF3˙+[g= 2.014, a(19F)= 1.3 G, ‘a(33S)’= 8.6 G], which suggested that spectra long assigned to 1,2-dithiete cations are in fact due to 1,2,3-trithiolylium cations. This is supported by the ESR spectrum of MeO2C[graphic omitted]CO2Me˙+, which consisted of a singlet at g= 2.017, with two sets of 33S satellites in a 2:1 intensity ratio, with very similar 33S coupling constants (8.0 and 8.9 G). The salt F3C[graphic omitted]CF3AsF6 is reduced by KI to give a mixture of neutral cyclic polysulfides including F3C[graphic omitted]CF3(43%) and the previously unknown F3C[graphic omitted]CF3(23%). Attempts to oxidise F3C[graphic omitted]CF3˙+ with AsF5 were unsuccessful.

Preparation and crystal structure of the paramagnetic solid F3CCSSSCCF3AsF6: implications for the identity of RCSSCR˙+

An initial virgin plasticine-like poly(3-octylthiophene) (P3OT) and this sample modified by annealing and recrystallization were investigated at X-band (10 GHz) and mainly at D-band (140 GHz) electron paramagnetic resonance (EPR) in a wide temperature region. Paramagnetic centers with anisotropic magnetic-resonance parameters were proved to exist in all polymers, namely, mobile polarons whose concentration and susceptibility depend on the temperature and the polymer treatment. Superslow torsional motion of the polymer chains and layers was studied by the saturation transfer method at D-band EPR. Spin-spin and spin-lattice relaxation times were measured separately by the steady-state saturation method at the same waveband EPR. Intrachain and interchain spin diffusion coefficients and conductivity due to polaron dynamics were calculated. It was shown that the charge transport in P3OT is determined by the strong spin-spin interaction and is stimulated by torsion motion of the polymer chains. The total conductivity of P3OT is determined mainly by dynamics of paramagnetic charge carriers. Magnetic, relaxation and dynamics parameters of P3OT were also shown to change during the polymer treatment.

EPR Study of Spin and Charge Dynamics in Slightly Doped Poly(3-octylthiophene)

Aus den ESR-Spektren spezifisch mit 13C und 33S markierter Derivate werden die Kopplungskonstanten dieser Kerne im Di-tert-butyl-monothiosemidion- (1−˙) und -dithiosemidion-Radikalanion (2−˙) bestimmt. Letzteres entsteht bei der Einelektronen-Reduktion von 3,4-Di-tert-butyl-1,2-dithiet. Aus den Kopplungs-konstanten – insbesondere den anisotropen Werten – werden die Spindichten erhalten. – Mit Hilfe des semi-empirischen MNDO/Cl- und MINDO 3/Cl-Verfahrens unter Einbeziehung der Konfigurationswechselwirkung (Cl) werden die Geometrien der betrachteten Molekule sowie theoretische Spindichten ermittelt und den experimentellen Daten gegenubergestellt.



Coupling constants of the 13C and 33S nuclei are determined from the ESR spectra of specifically labelled di-tert-butyl-monothiosemidione (1−˙) and -dithiosemidione (2−˙) radical anions, the latter being formed on one-electron reduction of 3,4-di-tert-butyl-1,2-dithiete. Spin densities are calculated from these coupling constants and, especially, from the anisotropic values. – Using the semi-empirical MNDO/Cl and MINDO3/Cl methods including configurational interaction (Cl) the geometries and theoretical spin densities are determined and discussed in terms of the experimental values.

Thioketyle, 9 ESR‐Untersuchungen und semi‐empirische MO‐Rechnungen an aliphatischen Mono‐ und Dithiosemidion‐Radikalanionen

In Reaktionsgemischen von Acetylenen RC CR (1) mit R H, CH3, C2H5, C3H7, C4H9, C(CH3)3, C6H5 mit ClSSCl/AlCl3/H2CCl2 oder mit S8/SbCl5/H2CCl2 lassen sich bei 250 K zunachst 1,2-Dithiet-Radikalkationen R2C2S2⊕ (2a – g) und nach Erwarmen auf 300 K zusatzlich 1,4-Dithiin-Radikalkationen R4C4S2⊕ (3) ESR-spektroskopisch nachweisen. Ihre Erzeugung gelingt auch durch Umsetzung von 1,2-Dichlorethen- oder 1,1,2,2-Tetrabrom-ethan-Derivaten mit Na2S2/AlCl3/H2CCl2, die sich zur 33S-Isotopenmarkierung eignet. Nach geometrie-optimierten closed und open shell MNDO-Berechnungen ist sowohl fur H2C2S2 wie fur H2C2S⊕ die Vierring-Struktur bevorzugt; hohe Spindichte in der Disulfid-Gruppierung erklart die beobachteten grosen g-Faktoren und 33S-Koppungskonstanten.



Radical Ions, 71. Oxidative Sulfurization of Acetylenes to 1,2-Dithiete and 1,4-Dithiine Radical Cations



In reaction mixtures of acetylenes RC CR (1) with R H, CH3, C2H5, C3H7, C4H9, C(CH3)3, C6H5 and ClSSCl/AlCl3/H2CCl2 or S8/SbCl5/H2CCl2 at 250 K first 1,2-dithiete radical cations R2C2S2⊕ (2a – g) and after warming to 300 K in addition 1,4-dithiine radical cations R4C4S2⊕ (3) are characterized ESR spectroscopically. Their generation can also be accomplished by the reaction of 1,2-dichloroethene or 1,1,2,2-tetrabromoethane derivatives with Na2S2/AlCl3/H2CCl2, a method well suited for 33S isotope marking. According to geometry-optimized closed and open shell MNDO calculations, the preferred structures both for H2C2S2 and for H2C2S⊕ are four-membered rings; high spin density in the disulfide moiety allows to rationalize the observed large g values and 33S coupling constants.

Radikalionen, 71. Oxidative Schwefelung von Acetylenen zu 1,2-Dithiet- und 1,4-Dithiin-Radikalkationen

Novel 1,2-dithiete derivatives R2C2S2 with R = [sbnd]C(CH3)3 and [sbnd]C(CH3)2[sbnd]CH2[sbnd]CH2[sbnd]CH2[sbnd]C(CH3)2[sbnd] are readily oxidized by the one-electron transfer system AlCl3/H2CCl2 to their radical cations. The single line ESR spectra, on high amplification, exhibit 33S satellites in natural abundance. Both the ESR data, i.e. rather large g values and 33S hyperfine coupling constants as well as MNDO closed and open shell calculations for the parent molecule H2C2S2 illustrate that spin and positive charge are predominantly located in the SS bridge of the four-membered ring.

Arin Schütz

Papers

Radical ions 561,2 one-electron oxidation of 1,2-dithiete derivatives